Ducati916: said to myself...man, these things are pure ***...felt that way for several days. Now I've come to understand that the clubs are what they are
The difference between Med/High and High is huge in irons, I'm surprised you were even playing those Med/High irons, as good as you are. The easiest way to reconcile the difference in play between the 2 models is to think of the shot arc. The Med/High one is flatter, will come in hotter and would need a lot of spin to control the rollout.
Conversely, High shots drop from a steeper angle, have less rollout so not so much spin is needed and because they're in the air longer, the wind is going to push the shot around more. The arc difference is the biggest reason you're seeing that bigger yardage drop when you choke down.
You're in a much better place with those new irons, just think a little differently on your approaches. Learn their carry and then use partial spin to control what happens after the shot lands. :-)